Abstract:

Barley leaf stripe, caused by Pyrenophora graminea, significantly reduces yield. Polygalacturonase, a key fungal pectinase, facilitates cell wall degradation for nutrition acquisition and colonization. To determine whether P. graminea contains polygalacturonase (PgPG)-encoding genes and their role in pathogenicity, four PgPG genes (PgPG1-PgPG4) were identified in the P. graminea genome. Quantitative RT-PCR revealed that PgPG1 had the highest inducible expression during barley infection, suggesting its critical vital role in pathogenesis. PgPG1 was silenced and overexpressed in P. graminea QWC (wild-type) using CaCl₂-PEG4000-mediated protoplast transformation. The PgPG1 RNAi mutants exhibited slower growth, while overexpression mutants grew faster. Relative to the wild-type, the disease incidence of Alexis, a highly susceptible barley variety, decreased by 62.94%, 42.19%, 45.74%, and 40.67% for RNAi mutants, and increased by 12.73%, 12.10%, 12.63%, and 10.31% for overexpression mutants. Pathogenicity analysis showed decreased disease incidence with PgPG1 RNAi mutants and increased severity with overexpression mutants. Trypan blue staining and polygalacturonase activity assays confirmed that overexpression mutants caused more severe damage compared to wild-type and RNAi mutants. These findings indicate that PgPG1 plays a vital role in the pathogenicity of P. graminea in barley and has great potential as a pathogen target gene to develop a durable resistance variety to P. graminea.